Re-gearing a ford bronco?

I have a 1986 ford bronco with a 5.0 liter EFI and a AOD automatic transmission, I'm planning on putting a 4 inch lift with 33" tires on it pretty soon but I need to re-gear my axles because I only have 3.55's for some reason. I was wondering what kind of gears I should get and about how much it would cost, I'm not planning on doing anything huge but just something that would give me more low end power, thnaks.